The invention relates to a process for the preparation of a castable hot mixture of bituminous concrete. Such concrete is often used for strengthening the banks of waterways and for roadway surfaces. As is well known, it comprises a mixture of filling material (such as sand, lime, and/or stone pieces e.g. of dimension from 2 mm up to 20 mm) and a fusible bitumen that, in a hardened state, binds the filling material together. "Bitumen" is to be understood as a mixture of mainly hydrocarbons with residual impurities, as obtained as residues from refining coal or petroleum, such as pitch or tar or asphalt. The chosen bitumen is adapted to be sufficiently hard for the temperatures at which it is exposed for use, which in general is a temperature below 40 C., and further adapted to be sufficient liquid at the mixing temperature, so as to be mixable with the filling material during mixing, and to keep sufficiently soft during a subsequent time after dumping, so that it can be deformed and compacted into its final form in which it has to harden. A suitable mixing temperature ranges between 80.degree. C. and 200.degree. C. Mixing below 80.degree. C. leaves insufficient free time between dumping and compacting, and above 200.degree. C. the process is less economical and less practical for handling the hot mixture. A mixture of such bituminous concrete at such mixing temperature is meant when referring hereinafter to a "castable hot mixture of bituminous concrete".
In order to strengthen the bituminous concrete, it is known, e.g. from U.S. Pat. No. 4,382,988, to introduce into the mixture a multiplicity of steel wire pieces, adapted for strengthening the bituminous concrete after its solidification, and mixing the steel wire pieces into the mixture. There are already steel wire elements on the market, adapted for reinforcement of cementitious concrete, in the form of bundles of such steel wire pieces that are held together in the bundles by a binding substance adapted to disintegrate by water when mixed into a wet cementitious concrete. Such wire bundles are introduced into the wet mixture of cementitious concrete, they disintegrate into individual wire pieces by the water of the mixture and by the mixing movement, and, by further mixing, the individual wire pieces come to be equally distributed in the mixture. Owing to the introduction in the form of bundles, it is avoided that the individual wires come to conglomerate into balls instead of being equally distributed. Such a mixing method and a bundle adapted has for this method been described in U.S. Pat. No. 4.314.853. Such bundles are now produced in mass by a method in which a number of wires are bundled and then glued together by applying a water emulsion of the glue (that, after drying, will re-emulgate or dissolve later again in the cementitious concrete) and then the bundles are caused to dry in a drying furnace. Then bundle is then finally transversally cut into pieces of short bundles, as described in U.S. Pat. No. 4.284.667. A known glue for that use is a glue of about 75% polyvinyl-acetate dispersion with a softening agent and with about 25% of a glue that is soluble in water, such as polyvinylalcohol or ethylene-vinyl acetate.